Light-switch seizure control? In a bright new study, researchers show how

Can an epileptic seizure be stopped with the flick of a light switch? Stanford neuroscientist John Huguenard, PhD, seems to have done just that, albeit in rats.

In a just-published Nature Neurosciencestudy, Huguenard’s lab has shown that a deep-brain structure called the thalamus plays a key role in epileptic seizures that are the all-too-often consequence of a stroke affecting the brain’s cognition-oriented outermost layer, the cerebral cortex. By neurological standards, the thalamus and cerebral cortex are miles apart (a few inches, really, but that’s a lot). But one of the former’s chief jobs is packaging all kinds of sensory information and delivering it to the higher brain centers in executive-summary form. As a result, the thalamus, itself relatively compact, connects to a broad expanse of cerebrocortical real estate via myriad two-way nerve pathways.

Huguenard and his colleagues bioengineered rats so that the nerve fibers in one of those bidirectional nerve pathways would respond to pulses of yellow laser light by refusing to transmit nervous impulses until the yellow light stopped. (This kind of procedure, pioneered by Stanford psychiatrist/bioengineer Karl Deisseroth, MD, PhD, is known as optogenetics and is rapidly becoming a widespread biological-research tool.)

Next, Huguenard’s team induced strokes in a specific area of these rats’ cerebral cortex that processes touch, pain, heat and related sensations. As expected, about a week or two afterward the rats started experiencing frequent seizures. But the scientists had implanted a device in the rats’ thalami that could both monitor the brain waves characteristic of such seizures and, on detecting them, automatically deliver a pulse of yellow light to the portion of the thalamus that communicates with the stroke-affected part of the cerebral cortex.

The result: As soon as a seizure started, the device pinged just the right spot in the rat’s thalamus with yellow light, causing the nerve tracts leading to the stroke-injured area to go on strike and shut the seizure down.

The inevitable question: Could this approach ever be used in people? In the course of writing my news release on this study, I put that question to Huguenard:

“This is not something that’s going to happen today or tomorrow,” he said. “It would require inserting genes into people’s living brain cells. And we’re still a ways from being able ensure the safety of gene therapy. This would also require being able to produce a reliable, battery-operated device that could be permanently implanted in the brain.”

But he also said that in a decade or so, what sounds like science fiction today may be a reality.